I deeply regret that due to the last lingering infection of pneumonia, I’m not going to be able to be with you physically at this celebration, at this place on the most important day in the history of science.
When I was asked by the British Council to give this brief introduction I considered it and even by video I always will consider it a high moment of my life and for that, I’m very grateful.
In 1869, ten years after the publication of The Origin of Species, Darwin wrote his close friend, the great botanist Joseph Hooker, as follows:
“If I lived twenty more years and was able to work, how I should have to modify the Origin, and how much the views on all points will have to be modified! Well, it is a beginning, and that is something.”
Darwin lived 13 more years after writing that letter to Hooker, and he did manage to modify the theory of evolution by natural selection, by expanding it in The Descent of Man in 1871 to include human origins, and in The Expression of the Emotions in Man and Animals in 1872 to address the evolution of instinct. And thus, if we add his first book, the Voyage of the Beagle, was completed what can be fairly called the four great books of Darwin, although he authored many other influential articles and books during his career.
Great scientific discoveries are like sunrises. They illuminate first the steeples of the unknown, then its dark hollows. The four major books have spread light not just on the living world but, fundamentally, the human condition. They have not lost their freshness: more than any other work in history’s scientific canon, they are both timeless and persistently inspirational.
The 150 years ensuing after the publication of the Origin has been a time of enormous growth of the Darwin heritage. Joined with molecular and cellular molecular biology, that accumulated together knowledge that is today the substance of biology. Its centrality justifies the famous remark made by the evolutionary geneticist Theodosius Dobzhansky, the foremost of the modern synthesizers of the 20th century. He said famously in 1973, “nothing in biology makes sense except in the light of evolution.”
In fact, nothing in science as a whole has been more firmly established by interwoven factual information, or more illuminating than the universal occurrence of biological evolution. Further, few natural processes have been more convincingly explained by evolution through natural selection, or as it is popularly called still, Darwinism.
The four books of Darwin, when read as a set chronologically, flow as a well-wrought narrative, tracing the development of Darwin’s thought across almost all of his adult life. The first, Voyage of the Beagle, is one of literature’s great travel books; it’s richly stocked with observations of the kind that were to guide the young Darwin in his evolutionary worldview. Next comes what he called the “one long argument” for evolution by natural selection, arguably and I believe, history’s most intellectually important book if judged on a global scale of impact. The Descent of Man then addresses the burning topic foretold in The Origin of Species, when Darwin ventures laconically that “light will be shown on the origin of man and his history,” By the time of the writing of the Descent, Darwin was confident that natural selection would prevail, and he delivers his conclusions forthrightly.
Finally, in The Expression of the Emotions in Man and Animals, Darwin draws close to the heart of the matter that concerns us all as a species: the origin and nature of mind, what Darwin called the “citadel”, that he could see but knew that science at the time could not conquer.
The chronicle of Darwin’s life in the four great books was a script for genius. It began in the voyage of the Beagle. The ship was commissioned by the British government to conduct a coast and geodetic survey around South America. It took five years, from 1831 to 1836, and ended up circumnavigating the globe.
I as you to imagine. For a 21-year-old man, newly escaped from Cambridge University, to leave for 5 years and suffer no television, no radio, no newspapers, no contact of any kind except months-old letters delivered at infrequent ports of call. Now set before him is something far better: an unexplored world to navigate and record for history, with unimaginable discoveries awaiting at every turn. For a young naturalist launched upon such a great voyage, and the vast majority of the plants and animals on Earth still unknown in science, with all the specimens he could collect valuable to science, and with all of the observations he made worth recording, and not least with no duty except gentleman companion to the captain and the ship’s naturalist, the world was Charles Darwin’s to possess.
Then, after a long gestation, came On the Origin of Species. Evolution by natural selection is perhaps the only one true law unique to biological systems, as opposed to non-living physical systems, and in recent decades it has taken on the solidity of a mathematical theorem. It states, to put it in extremely simple terms, that if a population of organisms contains multiple hereditary variants in some trait (say, red eyes versus blue eyes in some bird population), and if one of these variants succeeds in contributing more offspring, breeding offspring, to the next generation than the other variants, the overall composition of the population changes, and evolution has occurred. And, if new genetic variants appear regularly in the population (by mutation or immigration), evolution never ends.
The full importance of Darwin’s theory can be better understood by recognizing that modern biology is guided by two overwhelmingly powerful and creative ideas. The first is that all biological processes are ultimately obedient to, even though far from fully explained by, the laws of physics and chemistry. The second is that all biological processes arose through the evolution by the process of natural selection. The first principle is concerned with the how of biology, how the machine of the organism works. The second is concerned with the ways the systems adapted to the environment over periods of time long enough for evolution to occur—in other words the why of biology.
Knowledge addressing the first principle is called functional biology, and that addressing the second principle is called evolutionary biology. If a moving automobile were an organism, functional biology would explain how it is constructed and operates, while evolutionary biology would reconstruct its origin and history – how it came to be made and its journey thus far.
The impact of the theory of evolution by natural selection, nowadays grown very sophisticated at all levels of biological organization from molecules and cell up to ecosystem, has been profound, and its implications have reached to all of life and all dimensions of human existence. To the extent that it can be upheld, and the evidence to date has done so compellingly, we must conclude that life has diversified on Earth autonomously without any kind of external guidance. Evolution in a pure Darwinian world has no goal or purpose external to itself. The exclusive driving force is random mutations sorted out by natural selection from one generation to the next. We are on our own, it implies, we are one with the biosphere, but we are also free, thus wholly the masters of our own fate. That is the central philosophical contribution of The Origin of Species.
Twelve years after On the Origin of Species was published, Darwin, in The Descent of Man, dropped the other shoe. Victorian society, whose wrath Darwin had so feared as to hold back the publication of the Origin until 1859, might not have been entirely scandalized by the descent of plants and animals, but they were quite unprepared to accept the descent of man from as Darwin put it, delicately put it “some preexisting form”, and they were most certainly scandalized at the idea of apes as ancestors, as the evidence unfortunately for Victorian society suggested from the very start.
Yet Darwin had to take that step. It was implicit from the premise that evolution is universal. The indelible stamp of evolution, as he called it, is everywhere to be seen in human anatomy and all we know of its evolution. In 1871, Darwin and other evolutionists lacked the smoking gun: there was no fossil evidence. A century of research, however, has turned up an abundance of prehuman and early human remains, enough to establish the broad outline and many of the early detail of the origin of our own species. The family of man, as it turns out and Darwin guessed, originated in Africa and spread out over the rest of the world in successive waves. The line antecedent to the human clade evidently split about 6 million years ago from the separate line leading to our closest living relatives, the chimpanzees.
The Expression of the Emotions in Man and Animals, the final piece of Darwin’s tetralogy, is both an old-fashioned descriptive treatise and the most modern of Darwin’s major works. On the one hand it provides a straightforward catalog of human postures and facial expressions that might have been written in past centuries. On the other hand, this book is rich and accurate enough in interpretation to serve as part of the foundation of modern psychology. Darwin is, in Konrad Lorenz’s words, the “patron saint” of that discipline. His pioneering contribution was this: he treated emotions and their manner of expression as products of evolution. The instincts, and as such they have evolved by natural selection in essentially the same manner as traits and anatomy can be studied in a manner of analytic and synthetic biology. In one sense, reaching to the heart of human self-esteem, that was a move as daring as The Origin of Species itself.
The four great books of Darwin, and especially the pivotal one we celebrate today were put together by another innovation of the master naturalist. He gleaned information not only from existing literature and his own experience, but also from a global network of correspondence. In an effort worthy of the purposes of the British Council, he drew information and concepts from around the world, organized them, and distributed them back to the global culture. No-one has pulled that feat off in biology since.
At its foundation, biological knowledge conforms to the two principles I’ve just mentioned was arguably with enough firmness to be seen routinely as scientific laws. That is, they are all-inclusive and with no proven exceptions, and their consequences can be followed wide and deep. The first law says that all the entities and processes defining life are ultimately obedient to the laws of physics and chemistry. The second law, still in contention due to claims for counter-examples, has that all the entities and processes that define life, and all the diversity of life, have evolved by natural selection.
Modern evolutionary theory, rooted now in molecular genetics and thereby consistent with the first law of biology, begins with the distinction between the units of heredity and the targets of natural selection. The units are the genes, respectively the base-pair sequences forming their codes, their degree of duplication in the genome by tandem repeat sequencing, their location in the genome, and the interaction of their products during epigenesis. The targets of the natural selection process are the phenotypes, that is, the outward traits prescribed by that genetic infrastructure.
Natural selection is also multilevel, operates at different levels. That is, a phenotypic target of natural selection can exist at any level of biological organization, from macromolecules to chromosomes to eukaryotic cells to multicellular organisms, and even to organized social groups, and populations of groups and individuals, and finally and arguably, entire ecosystems.
I make this rather technical point to lead into what I believe is the future path of biology. Multilevel selection typically places selection at adjacent levels in opposition. To go on up to say a multicellular organism or a complex society, requires some degree of altruism on the part of individuals at the lower level. It is promoted by selection at the level of organisms that make up the groups. Such major transitions across levels of organization have occurred very rarely in evolution and taken long periods of time to be achieved even once, and this is a phenomenon that we, evolutionary biologists, have not yet explored in enough depth. The origin of eukaryotic organisms, for example, took over half the known history of life to be reached, from the beginning over 3.5 billion years to 1.5 billion years ago. Multicellular organisms and animals in particular were not added for more than another half-billion years. The origin of insect superorganisms, in particular the tightly knit colonies of ants and termites or their equivalent, was not attained until well into the late Jurassic to very early Cretaceous Periods 200 to 140 million years ago.
I believe that in this century it is in the major transitions of evolution that biology will predominantly dwell. The Age of Reduction in biology has largely passed. While enormous amounts of new information will continue to be yielded by the cleavage and analysis of complex systems, the big problems in each discipline are those that require an exactitude of synthesis, or more accurately, recreation of reduced systems broken down by analytic research. As more biological systems are understood, and with them the major transitions, common principles of emergent evolution should become apparent. There appears to be no aprioristic way to create such a unified theory of biology at the present time. It awaits far more empirical information than we now possess, requiring immense amounts of hard work with real organisms.
Contemporary biology has long been addressed by two very different strategies of research. The first strategy follows the dictum that for every problem in biology there exists an organism ideal for its solution. The bacterium E-coli has thus triumphed for molecular genetics, the nematode C-elegans for the neuronal basis of behavior, the honeybee for the instinct and self-organization of animal societies, and human beings for the conscious mind.
If those scientists faithful to this dictum are called the problem solvers, the second tribe of scientists may be called the naturalists. The research strategy of the naturalists is the inverse of the strategy of the problem solvers. It is that for every organism there exists a problem for which the organism is ideally suited. The procedure of the naturalist is to adopt a group of species, such as conifers, diatoms, orb-weaving spiders, and fall in love with those organisms, and learn as much about them as possible across all levels of biological organization, from the genes to their place in the ecosystems.
Problem solvers, at work mostly in the laboratory, explain the proximate causes of biological phenomena, usually those visible only at a microscopic level. In other words they discover how the system works. Naturalists, their counterparts working typically in the field, but experimentally in the laboratory also, stress the adaptation of biological phenomena to the environment, the why in its attempted full explanation.
Although the two approaches have seemed at times to represent independent cultures, in fact they are complementary and can with more information be fitted nicely together. The boundaries today are in fact being erased. Scientific naturalists, working as organismic and evolutionary biologists, use the methods of molecular and cell biology, while molecular and cell biologists grow more prone to address patterns of diversity and evolution. With increasing frequency the two tribes of biology collaborate in research projects.
Now at the risk of oversimplification, it can be said that the naturalists discover the problems in nature that the problem solvers solve.
The trajectory of a unified biology can therefore be visualized as T-shaped. The horizontal arm is biodiversity at the level of species and genetic strains within each species. One vertical arm is the model species of the problem solver, reaching from the populations that constitute the species or strains down through the levels of biological organization. At the present, perhaps fewer than a hundred such model species are in full practice of examination; in a decade or two there will be thousands and then tens of thousands. The process will accelerate as DNA sequencing grows ever faster and cheaper.
The more the two-dimensional array of knowledge is filled in, the more the gaps in knowledge and the most promising new directions of research will become apparent. At the same time, paleontology and phylogenetic analysis will add the dimension of time.
A unified biology to conclude is a goal worth thinking about, even if it may still be far from our grasp. Biologists are stretching causal explanations across wider segments of the levels of biological organization and in broader arrays of species. In so doing they are melding together explanations of function and adaptation, as well as molecules and cells with organisms and species. As a result the emphasis in research is shifting from one or two levels of biological organization to the transitions between these several levels.
The unified biology that Darwin made possible will in the twenty-first century be the one that maps the pathways from molecules to ecosystems in unbroken transits of causal explanation. It will disclose the still unimagined commonalities, if such exist, among the evolutionary transitions. It will also provide insight into whatever different genetic codes and transitions are possible, and even which of these might exist on other worlds. The Origin of Species defined the path of a unified biology. This great book led to a renewal of the Enlightenment, and, at last, brought within reach an authentic science of man.
Thank you very much.
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